In many electronic appliances (e.g. telephones, answering machines, audio cassette and mini-disc recorders, etc.) integrated microphones are provided to capture acoustic signals. Generally, electret microphones are used because of their low cost and good performance. A microphone gasket or boot is usually used to isolate the microphone from the structure of the appliance and to couple the sound effectively to the microphone. The construction of such microphone gaskets ranges from very simple (e.g. a tube) to very complicated (e.g. multi-part arrangements such as found in high quality telephone handsets).
In simpler designs, a cloth facing is often used to damp the tube resonances that develop in some microphones. More complex designs utilise a piece of fabric with desired acoustical resistance mounted to a part that is inserted in the appropriate place to provide the desired acoustical damping. In some other designs, reticulated (i.e. open cell) foam is used to provide the acoustical damping.
Some lower cost microphones are fabricated without any cloth facing while other microphones incorporate a cloth facing that provides virtually no acoustical damping. When either of such microphones are used, a complex gasket must be added which incorporates a suitable acoustical damping material or else the acoustical performance will suffer.
One further problem with prior art designs is that in order to obtain repeatable acoustical responses using a fabric, foam or other acoustically resistive material the manufacturing process must be very tightly controlled. This adds to the expense of the microphone and ultimately the appliance in which the microphone is used (e.g. telephone set, answering machine, etc.).